Method of rerouting telecommunications traffic

Abstract

This invention relates to a method of establishing connections over a public switched telephone network to a customer whose telephone number is in a block associated, for routing purposes, with a first telephone switching system, but who is actually served by a second telephone switching system. The facility for carrying out this method is desirable in order to serve customers who need the advanced functions of a digital switching system, who are currently served by an analog switching system, and do not wish to have their telephone number changed when they switch to being served by the digital switching system. In accordance with the invention, a common channel signaling initial address message is sent to the first system. The first system translates the telephone number of that initial address message and finds that the customer for that telephone number is now served by a second switch. The first switch then sends a release message containing the identification of the second switch back to the source of the initial address message. The source of the first initial address message then sends a second initial address message to the identified second switch and the call connection can now be established to the customer served by the second switch. During the time the customer is being moved from the first switch to the second switch, one of the two returns a "temporarily out of service" type of announcement.

I claim: 
     
       1. A method of establishing a telephone call connection to a customer, served by a first telephone switching system for switching telephone communication traffic or a second telephone switching system for switching telephone communication traffic, whose telephone number is one of a block served by said second telephone switching system, the method comprising the steps of: transmitting a first setup message from a third telephone switching system for switching telephone communication traffic of a public switched network to the second telephone switching system;   responsive to receiving said first setup message, determining which telephone switching system serves said customer identified by said telephone number;   if said determining indicates that said customer is served by said second telephone switching system, establishing a connection to said customer in said second telephone switching system;   if said determining indicates that said customer is served by said first telephone switching system, transmitting a release message, the release message comprising the identification of the first telephone switching system, to the third telephone switching system; and   responsive to receiving said release message, transmitting a second setup message from the third telephone switching system to the first telephone switching system for establishing a call connection from the third telephone switching system, to the first telephone switching system.   
     
     
       2. The method of claim 1 wherein said transmitting steps comprise the steps of transmitting over a data network. 
     
     
       3. The method of claim 2 wherein said data network is a common channel signaling network. 
     
     
       4. The method of claim 3 wherein said common channel signaling network comprises a plurality of signal transfer points. 
     
     
       5. The method of claim 1 wherein said setup messages are initial address messages. 
     
     
       6. The method of claim 1 wherein said step of transmitting a release message comprises the steps of: translating a telephone number received in said first setup message to fetch data for said telephone number;   determining whether said data comprises data indicating that said telephone number is served by a telephone switching system other than said second telephone switching system; and   if said determination indicates that said telephone is served by a telephone switching system other than said second telephone switching system, formulating a release message comprising the identification of said telephone switching system other than said second telephone switching system.   
     
     
       7. The method of claim 1 wherein said first, second, and third telephone switching systems are part of a public switched network. 
     
     
       8. The method of claim 1 further comprising the steps of: testing whether service to the telephone number has already been activated in said first telephone switching system, and, if not, returning an announcement to a caller of said call.   
     
     
       9. A method of establishing a telephone call connection to a customer, served by a first telephone switching system for switching telephone communication traffic or a second telephone switching system for switching telephone communication traffic, whose telephone number is one of a block served by said second telephone switching system, the method comprising the steps of: transmitting a first setup message from a third telephone switching system for switching telephone communication traffic of a public switched network to the second telephone switching system;   responsive to receiving said first setup message, determining which telephone switching system serves said customer identified by said telephone number;   if said determining indicates that said customer is served by said second telephone switching system, establishing a connection to said customer in said second telephone switching system;   if said determining indicates that said customer is served by said first telephone switching system, transmitting to the third telephone switching system a release message, the release message comprising data for identifying the first telephone switching system; and   responsive to receiving said release message, transmitting a second setup message from the third telephone switching system to the first telephone switching system for establishing a call connection from the third telephone switching system, to the first telephone switching system.   
     
     
       10. A method of establishing a telephone call connection to a customer, served by a first telephone switching system for switching telephone communication traffic or a second telephone switching system for switching telephone communication traffic, whose telephone number is one of a block served by said second telephone switching system, the method comprising the steps of: transmitting a first setup message from a third telephone switching system for switching telephone communication traffic of a public switched network to the second telephone switching system;   responsive to receiving said first setup message, determining which telephone switching system serves said customer identified by said telephone number;   if said determining indicates that said customer is served by said second telephone switching system, establishing a connection to said customer in said second telephone switching system;   if said determining indicates that said customer is served by said first telephone switching system, transmitting to the third telephone switching system a release message, the release message comprising data for identifying that said customer has been moved from said second telephone switching system to said first telephone switching system; and   responsive to receiving said release message, transmitting a second setup message from the third telephone switching system to the first telephone switching system for establishing a call connection from the third telephone switching system, to the first telephone switching system.